Drawn intermingled yarn



Sept. 22, 1970 H, J, MARRlNAN ETAL 3,529,413

DRAWN INTERMINGLED YARN Original Filed Oct. 16, 1963 I Fg United States Patent O U.S. Cl. 57-140 1 Claim ABSTRACT F THE DISCLOSURE A drawn yarn of intermingled filaments of polyethylene terephthalate in which the filaments of the yarn are integrated by random intermingling to give 6-12 intermingled places per meter as a cohesive density when side wound in the absence of twist on a bobbin. The yarn is of such uniformity as to give a zero incidence of dyeflecks.

This application is a continuation of application Ser. No. 316,766, filed Oct. 16, 1963, now abandoned.

This invention relates to a process for drawing synthetic linear polymer filaments which are in an undrawn state, defined in that the natural draw ratio at room temperature makes them capable of elongating at least twice their length.

Many processes for drawing synthetic linear polymer filaments are known, processes commercially acceptable comprise the use of heated snubbing pins followed by heated plates. Other processes comprise the use of heated feed rolls followed by heated plates or for certain requirements only a snubbing pin or a roll which may or may not be heated. In these and other drawing processes proposed hitherto, neighbouring filaments in a yarnconstrain each other with the result that there is interaction between them and, furthermore, this interaction between individual filaments can be enhanced by surface tension forces when any liquid such as spin finish is present. This interaction hinders the drawing of individual filaments in a yarn with the result that uniform drawing is difficult to achieve. Hitherto, a drawing treatment in which there is no such infiuence from neighbouring filaments has not been practised.

We have made the observation that ideally each filament should be drawn at a temperature appropriate to its own birefringence, and hence should be free of influence or constraint from neighbouring filaments at the critical position where the drawing is taking place. These objectives may be realised provided the filaments are sufficiently spaced apart when the drawing tension is applied, and the heat input is sufficient to engender drawing at or near the second order transition temperature, but before flow-drawing conditions occur.

We propose that the filaments should be spaced apart by fiuid jets, e.g. similar to the air ejector used in our B.P. 723,920, which claims a process for making a tow from a number of bundles of continuous artificial filaments which comprises subjecting the bundles to a treatment such that an electrostatic charge is induced on the filaments prior to or during the feeding of the bundles into a tube through which a current of air fiows, characterised in that the current of air is under a pressure of 60 to 100 lb. per square inch. In our British Pat. 758,398 a process is described for hot drawing filaments made from linear polyesters which are heated by one or more narrow streams of hot fluid such as steam, impinging on the filaments or like structures while being drawn. The steam jets in this prior patent are used under conditions such Patented Sept. 22, 1970 ICC as to cause heating and localising the draw zone in tows, without however causing any appreciable defiection of the filaments from their paths between the rolls, and so that the filaments are not deflected to catch protruding parts of the draw frame.

In the present case high velocity jets are used which cause turbulenece and which may be opposed to each other to impinge on filaments in yarn, so as to cause displacement of the filaments which are under drawing tension and which makes it possible for the filaments to be drawn at a temperature appropriate to their own birefringence, in this Way coupling between the filaments is reduced. The filaments which are in an undrawn state are defined in that the natural draw ratio at room temperature makes them capable of elongating them at least twice their length.

Thus according to our invention we provide a process for drawing undrawn synthetic linear polymer filaments between feed rolls and draw rolls when said filaments are in an undrawn state when entering the draw rolls, cornprising elongating the filaments at least twice their length subjecting said undrawn filaments to a high velocity turbulent fluid stream which is heated and capable of transferring heat to the individual filaments in an amount sufficient to localise the draw point, said turbulent heated fluid stream separating the individual filaments in the yarn at a critical position where drawing is taking place so that there is substantially no coupling between the filaments at the draw point. lIf desired heating of the filaments by the high velocity turbulent fiuid stream is continued by directing said fiuid stream in such a way that heat application is continued on to the yarn after the draw point. This may be done by providing means for surrounding the yarn, which reduce heat loss, e.g. a shroud or tube.

It desired the turbulent fluid stream in addition to its above function can be used to intermingle the filaments to produce a cohesive yarn and also to continue heating the filaments over a short interval which may extend as far as the draw rolls but we prefer not to exceed 2 inches, while continuing to apply said force and drawing tension, followed by winding or forwarding the drawn filaments after cooling substantially to room temperature, before being wound up. Under these conditions the filaments are drawn at a temperature appropriate to each individual birefringence.

The filaments before being wound up may be subjected to a continuous crimping operation. One such crimping operation may effectively be carried out by a unilateral heat treatment as disclosed in B P. 808,213 when the filaments are made potentially crimpable by passing them over a narrow surface heated to a temperature above the melting temperature of the filaments, followed by heat relaxing the filaments preferably in a hot air stream, before being wound up. These yarns have unusual properties including improved bulk and heat stability not obtainable by prior art methods. The narrow heated surface may be inserted after the fiuid stream before or behind the draw rolls and preferably before the wind-up and when the filaments are already in their drawn condition. Preferably the narrow surface is inserted behind the fluid stream in front of the drawing roll after the yarn has passed the idler roll associated with the draw roll.

Alternatively the filament may be crimped by false twisting. This may be done by inserting a false twist in the yarn either before the draw rolls as disclosed in B.P. 777,625 but with means to prevent the false twist from running back into the draw zone of the air jet device, and without a snubbing pin; or by inserting the false twist after the draw rolls but before the wind-up. In each case a heater is required to heat set the imparted false twist before the filaments are wound up.

The attached drawings illustrate preferred embodiments of the apparatus and description, of ourl invention.

FIG. l is a side view of a drawing apparatus with an air jet.

FIG. 2 is a more detailed sectional view of the air jet used in FIG. 1.

FIG. 3 is a false twisting device with heater for use in the apparatus of FIG. 1.

FIG. 4 is a heater for potentially crimping yarn for use in the apparatus of FIG. 1.

Referring to FIG. 1 undrawn yarn .1 coming from a spin bobbin 2 over pigtail guide 3 is passed in several loops round driven feed roll 4 with associated idler roll 5, then to a double air jet 6 fitted with air stream valve 7 and electric heater for the air 7a and reducing valve 7b. From the air jet the yarn is passed through a gap of air f ambient temperature before reaching the draw roll 8 driven at a faster speed to give the required draw ratio. The yarn is looped round the draw roll with associated idler roll 9 before passing to guide 10 and to be woundup with the ring and traveller 11 with a vertical traverse 11a on draw twist bobbin 12. Instead of a draw twist bobbin a side-wound bobbin wind-up may with horizontal traverse be used.

Referring to FIG. 2 which is a diagrammatic sectional view of an air jet device for use in a position as shown in FIG. l at 6 comprising air inlet tapering ducts 6a and 6b with a passageway 6c for the yarn.

If it is desired to produce a crimped yarn a heated narrow surface as disclosed in B.P. 808,213 or an indirectly heated narrow surface 16 (shown in FIG. 4) may be inserted in any one of the following positions marked B, C or D. (It should be appreciated that the narrow surface of FIG. 4 is shown in side view and is turned 90 for use in FIG. 1.) When contacting the narrow surface 16 shown in FIG. 4 the filaments become potentially crimped. Preferably they are heat relaxed in a heater tube (not shown) with hot air, before being finally wound-up.

Alternatively if it is desired to produce a false twist crimped yarn a false twisting device .14 shown in FIG. 3 may be inserted at B and in that case a baffle between the air jet device 6 may be provided to heat set the false twist imparted by the false twisting device 14 provided that the false twist is not allowed to run back into the .draw zone of the air jet device 6. This may be prevented by introducing a pin or a guide 13 or an idler roll behind the air jet device 6 and before the false twister such as 14 at B. Alternatively the false twisting device may be inserted at D but in that case the distance between the draw roll with associated idler roll S and 9 and the pigtail guide and the wind-up device must be sufficiently extended to make room for a heating device 15 suitable for heat setting the imparted twist from the inserted false twisting device 14.

We therefore also provide an apparatus suitable for carrying out the process of our invention comprising yarn supply means such as a spin bobbin, feed rolls for removing the yarn from the yarn supply means and for forwarding them to draw rolls with means for rotating the draw rolls at a surface speed at least twice that of the feed rolls, high velocity liuid jet means interposed between the feed rolls and the draw rolls with means for heating the fluid and means for controlling the uid temperature and pressure before it leaves the ud jet, and means for forwarding or winding the filaments.

We also provide an apparatus for continuously drawing and crimping synthetic linear polymer filaments in which a narrow heated surface such as 16 is inserted for contact with the filaments after the fluid jet means in front 0r behind the draw roll (such as 8) but before wind-up (such as 12).

If the apparatus is fitted with the narrow heated surface a device for heat relaxing the potentially crimped filaments may be provided which will heat the filaments and permit a required relaxation with further sets of driven rolls, preferably before the yarn is wound up.

In our process the drawing tension which may be used is 0.6 gram per denier at a draw ratio of l to 3.12 in the case of polyethylene terephthalate filaments; this drawing tension is greater at higher draw ratios and lower at lower draw ratios.

By textile processing performance we mean at least one of the following processing steps in which the yarns may be used without further insertion of twist or sizing when winding, coning, doubling, knitting, weaving or similar processes in which yarns are used for conversion into fabrics.

The synthetic linear polymer filaments which can be drawn according to the process of our invention may be chosen from one of the following fibre-forming polymers, polyesters derived from terephthalic acid, such polyesters containing minor proportion of a second component copolymerisable with the polyester, polyamides, particularly nylon and polyolens particularly those containing 70-100% of isotactic propylene.

The following description will serve to illustrate our invention.

The undrawn yarns were made by meltspinning polyethylene terephthalate, but it will be appreciated that undrawn yarns which have been meltspun from other synthetic fibre-forming polyesters may be similarly processed.

Polyethylene terephthalate undrawn yarn having a birefringence of 8.0 103 was unwound and passed through `a turbulent air zone created by high velocity air jets coming from a pressure vessel under 60 pounds per square inch pressure which Was heated with an electrical heater, regulated through a variable transformer to attain the desired temperature, the measurement being made by a thermocouple in the air duct after passing the heater. A conventional feed roll and separator roll was used to unwind the yarn from a yarn supply and it was then fed through the heated air device below which the yarn is taken up by a faster rotating draw-roll, the speed of which is adjustable to give a predetermined fixed draw ratio. Draw ratios of 1:3 to 1:4.5 have been used successf-ully at wind-up speeds between 100 and 800 meters per minute but there is no apparent reason why this device should not be operated at greater .wind-up speeds. Air temperature between 100 C. and 400 C. gave good results. Various types of air jets lwere tried in which the air impinged at right angles, obliquely or substantially parallel to the initial yarn axis. In addition, the yarn passageway may be fluted so that the air supplied to the device `may be made to exhaust preferentially through one end or the other. In this 'way a tensioning effect on the yarn is obtained.

A snubbing pin over which the yarn is passed, is known for drawing, and this is replaced in our drawing process with the iiuid jet, if desire'd and as illustrated in the examples.

Furthermore ordinary wear which may occur on the device in use does not materially affect its functioning. Indeed the size and finish of the element defining the yarn passageway are not critical and even minor irregularities have no detrimental effect. yRelatively short zones in which the yarn is under the influence of the high velocity air jet have been used successfully, having a length of 1A but longer lengths as defined above may also be used if preferred. Diameters at least 4 times that of the compact cross-section of the yarn may be used, the upper limit does not seem to be particularly critical and it is believed that tubes up to 100 times the yarn diameter are suitable.

EXPERIMENTAL RESULTS A series of trials are outlined below in which the inpfut yarn was undrawn polyethylene terephthalate of birefringence x10-3 and intrinsic viscosity/ 0.67. The yarn `was of total denier 156.7 before drawing, and had 24 filaments. Unless otherwise specified the yarn was drawn between rolls and their associated separator rolls to a draw ratio of 123.34. The high velocity fluid -jet comprised air as supplied to an air ejector at a pressure of 60 p.s.i. unless otherwise stated, and the temperatures quoted were in the supply line before expansion in the jets. The air ejector was positioned approximately half the ejector `was under a tension as required to effect drawing. All the examples specified were carried out at 1500 ft./min.

Example l In Example l the yarn twas drawn under tension of about 35 g. through an air ejector with a yarn passage- 'way length of 2 and opposed air jets in this instance at 180 C. to each other, centrally disposed in, and at right angles to the yarn passageway. The diameter of the yarn passageway was 0.070", and the jet diameter 0.050. The air temperature as supplied Iwas 150 C. The yarn produced was free of undrawn filaments as shown by dye-eck testing (24,000 ft. wound on a bobbin and dyed) and the following properties were found: shrinkage in boiling water 11.5%, extension at break 15.5%, tenacity 4.4 g.p.d. and cohesive density as shown by a needle displacement test 10.5 i.p.m. (intermingled places per meter when side-wound as a iiat yarn).

Example 2 In Example 2 the same input yarn was used, but with an air ejector of the following dimensions: yarn passageway length l and diameter 0.060". Air jet diameter 0.80. The configuration of the jets was as in Example 1, the air supply temperature was 230 C. The yarn produced was again free of undrawn filaments and had the following properties: Boiling water shrinkage 7.8%, extension at break 23.2%, tenacity 5.0 g.p.d., the yarn was integrated and cohesive to a density of 8.5 i.p.m., tested as before.

Example 3 The same air injector and yarn as for lExample 2. were used, but at an air pressure of 45 p.s.i.g. and a. supply temperature of 200 C. The yarn produced had a residual shrinkage of 12.4%, extension at break of 23.4% and a tenacity of 4.8 g.p.d

Example 4 The same air ejector and yarns were used, as in Ex. 2, but the air temperature and pressure were 200 C. and 80 p.s.i.g. respectively. The yarn had a tenacity of 4.9 g.p.d., extension at break of 17.4%, a coefficient of variation of denier of less than 1.5% and was free of undrawn filaments as before.

Example 5 Example 5 used a higher draw ratio of 3.8.2:1. The air ejector as in Example 2 lwas used to draw yarn at a temperature of air supply of 240 C. The yarn produced had a shrinkage of 9.8%, extension at break of 13.9%, tenacity of 5.96 g.p.d. and an integrated and cohesive density of 6.0 i.p.m.

Examples 6 and 7 Polyethylene terephthalate yarn of 0.67 intrinsic viscosity, 84x103 birefringence, dull 50/24 ,(denier/ilaments) was drawn at a draw speed of 1500 ft./min. using an air ejector yarn passageway length of 11A".

The angle of the air jets was 40 to the yarn passageway.

The yarn passageway diam. was 0.075", the air jet diameter .050 the temperatures for the air streams used and the resulting yarn properties are given in the following table.

In the above examples the filaments in the resultant yarns were sufficiently intermingled to significantly improve the weaving and knitting behaviour of the yarn, both when it `was wound on a draw twist spindle which inserted about 3%; turns per inch on the yarn, as well as when it was wound as a fiat yarn on a side windup, compared with yarns drawn without the fluid jets. Under the conditions of the test the yarns exhibited a reduced incidence of dye-hecks.

The coherence of the filaments in the yarns referred to in the examples is brought about by a process of false plating in which the filaments are separated and entangled in turbulent air streams. The amount of coherence due to this false plating can be measured, e.g. by inserting a needle in the yarn so that there is approximately an equal number of filaments on either side of the needle, the yarn being free from normal twist and any adhesive, and under a tension equal to 1/5 of the total denier, but not exceeding gm., and at a rate of traverse of the needle through the yarn of about 1 cm./ second. The number of cohesive points, due to the intermingling, per metre, is given by 50 divided by the mean distance travelled by the needle for atleast 50 tests.

It should -be appreciated that under certain conditions separation of the filaments by the air jets during drawing may be achieved without causing coherence in the issuing yarn or tow. This therefore also distinguishes our invention from B.P. 758,398.

If on the other hand the filaments are intermingledand it should be appreciated that this intermingling occurs after drawingnwe find that the textile processing performance of the yarn with the intermingled filaments is superior to that of an untwisted fiat yarn of the same composition, iilament count and denier; particularly if the cohesive density of the yarn is of the order illustrated in the examples. Yarns with 6-12 i.p.m. (intermingled places per metre) are desirable.

We claim:

1. Drawn intermingled yarn having a. cohesive density of 6-12 intermingled places per metre wherein the yarn is composed of filaments of polyethylene terephthalate and has a shrinkage in boiling water between 4 and 12%, an extension at break of between about 15 and 24%, a tenacity in excess of about 4 grams per denier, the lilaments in the yarn being integrated by random intermingling to give said 6-12 intermingled places per metre when side wound in the absence of twist on a side wound bobbin, said yarn Ibeing so uniform as to give zero incidence of dye-necks.

References Cited UNITED STATES PATENTS 3,069,836 12/1962 Dahlstrom et al 57-157 3,110,151 11/1963 Bunting et al. 57-157 3,303,169 2/1967 Pitzl.

FOREIGN PATENTS 758,398 10/ 1956 Great Britain.

JOHN PETRAKES, Primary Examiner U.S. Cl. X.R. 

